Daily active users (DAUs):1.04 billion, an increase of 17% year-over-year — and in line with expectations.

Along with strong growth across the board on those key numbers, Facebook also proved that it continues to strengthen its mobile business, noting that that's where it reels in 80% of ad revenue.

That's up from 69% at this time last year — and from 78% last quarter. For even more perspective, that's up from 23% in 2012.

That's tied to the fact that more of Facebook's users are accessing the social network from their smartphones. Mobile MAUs in December hit 1.44 billion, up 21% year-over-year, and mobile DAUs hit 934 million — up 25% year-over-year.

On the earnings call, COO Sheryl Sandberg emphasized that Instagram's ads business has been growing nicely, although the company declined to break out any specific revenue numbers.

She also said that she was pleased with the growth of Facebook video as well as its video-ad product. Users are now watching more than 100 million hours of video on the site per day.

Here are the other important numbers (emphasis added):

Costs and expenses of $3.21 billion, which is up 21% year-over-year, with R&D at$1.31 billion. But Facebook tightened its costs as a percentage of its revenue this quarter. The company's operating expenses were down sequentially and year-on-year in all categories.

However, on the earnings call CFO Dave Wehner warned investors to expect significant spending in 2016. He forecast non-GAAP expenses increasing between 45 and 55%.

Most of Facebook's revenue comes from North America and Europe — Facebook is killing it in the US — with only about 25% ($1.4 billion) coming from Asia-Pacific and the rest of the world. But those areas account for 65% of its monthly active users. The average revenue per user in those regions is still tiny, compared to in the US — $1.59 and $1.22, respectively, vs. $13.54 and $4.50 in the US and Europe.

Facebook recently made a big press push around its efforts in emerging markets and how it's optimizing its content and, importantly, its advertising to work well in areas of the world. But it seems that those efforts haven't shifted the average revenue-per-user numbers yet — although Facebook notes that currency headwinds also had an impact.

Here's a look at where Facebook's revenue comes from geographically:

Facebook

And as you can see, Facebook still makes the most money per user on US members:

Facebook

Here are some highlights from the earnings call:

Facebook CEO Mark Zuckerberg shared some other stats, like that people watched 100 million hours of video, more than 1 billion people used FB Groups in a single month, and 80 million people use Facebook Lite, the service optimized for lower-bandwidth.

He also said that WhatsApp has nearly 1 billion MAUs and that the company plans to roll out new ways to let businesses use it to communicate, like it has done with its other chat app, Messenger.

He ended his prewritten comments with a bit of sappiness, saying that since he had his daughter a few months ago, he spends more time reflecting on Facebook's legacy.

He said that thinking about how the company can "leave a better world for the next generation" is something that he thinks about "every day as we continue building Facebook."

Sandberg also said that Facebook is happy with the growth of Instagram's ad business, adding that 98% of top advertisers on Facebook also advertise on Instagram. Later in the call, she added that although some advertisers will likely choose to focus on one or the other, she expects that Facebook will also steal portions of their advertising budgets from other platforms.

"We really encourage people to measure their ROI and compare us to other platform," she said.

Facebook CFO Dave Wehner said that Facebook has increased its ad frequency this year, but that the average price per ad went up to (total impressions were up 29% and price per ad was up 21%). He also warned that 2016 would be another significant investment year, with non-GAAP expense guidance between 45% and 55%.

Following a question from investors, Zuckerberg also said that Facebook plans to keep experimenting with different ways to let businesses use Messenger. That's exciting for investors, who are clamoring for when Facebook will introduce a way to make money from the chat app.